The present invention relates to a device and a method for stabilizing a combination of a tractor vehicle, which may be a passenger vehicle or truck, and at least one semitrailer or trailer, which may be a truck trailer for a poassenger vehicle, e.g., a caravan.
German Published Patent Application No. 25 47 487 describes a device for stabilizing a vehicle having at least one guiding part and one pushing part. The pushing part is connected to the guiding part by a joint. The device has a measuring sensor for sampling the buckling angle that occurs between the guiding part and the pushing part. Furthermore, a measuring sensor is also provided for detecting the steering angle. The device includes an analyzer circuit which receives the signals from the two measuring sensors and generates an output signal when the buckling angle exceeds a certain angle size which depends on the steering angle. The certain angle sizes correspond to the buckling angles determined as a function of the steering angle and permitted on the basis of the prevailing driving situation. Furthermore, this device includes an apparatus for automatic control of a brake pressure of at least one axle of the pushing part, which is actuated according to the output signal of the analyzer circuit.
An object of the present invention is to provide an improved device and an improved method for stabilizing a combination of a tractor vehicle and at least one semitrailer or trailer.
This object is achieved by a device and by a method according to the present invention. To stabilize a combination of a tractor vehicle and at least one semitrailer or trailer, the semitrailer or trailer is braked (automatically) if the semitrailer or trailer buckles with respect to the tractor vehicle at a buckling rate whose value or absolute value is greater than a predetermined limit buckling rate. The trailer or semitrailer is then braked in particular when the following equation holds:
xcex94{dot over ("psgr")} greater than xcex94{dot over ("psgr")}lim, when xcex94"psgr" greater than 0
or
xcex94{dot over ("psgr")} less than xe2x88x92xcex94{dot over ("psgr")}lim, when xcex94"psgr" less than 0
where
xcex94{dot over ("psgr")} is the buckling rate of the semitrailer or trailer with respect to the tractor vehicle,
xcex94{dot over ("psgr")}lim is the limit buckling rate of the semitrailer or trailer with respect to the tractor vehicle and
xcex94"psgr" is the buckling angle of the semitrailer or trailer with respect to the tractor vehicle. The buckling angle of the trailer or semitrailer with respect to the tractor vehicle is defined here as
xcex94"psgr"="psgr"zxe2x88x92"psgr"a
xe2x80x83where
"psgr"z is the yaw angle of the tractor vehicle and
"psgr"a is the yaw angle of the trailer or semitrailer.
The buckling angle is measured according to German Published Patent Application No. 25 47 487, for example.
A better stabilization of the combination of a tractor vehicle and trailer or semitrailer is achieved by automatic braking of the trailer or semitrailer when the trailer or semitrailer buckles with respect to the tractor vehicle at a buckling rate which is greater than a predetermined limit buckling rate.
If there is a higher-level brake command, e.g., due to operation of the brake by the driver of the combination, then the trailer or semitrailer is considered as braked in the sense of the present invention only if it is braked more strongly than the tractor vehicle.
In an advantageous embodiment of the present invention, the trailer or semitrailer is braked if:
xcex94"psgr" greater than xcex94"psgr"*, when xcex94"psgr" greater than 0
or
xcex94"psgr" less than xcex94"psgr"*, when xcex94"psgr" less than 0
where
xcex94"psgr" is the buckling angle and
xcex94"psgr"* is the preselected setpoint buckling angle.
The combination is also stabilized in this way.
Another improvement in the stabilization of the combination is achieved in an advantageous embodiment of the present invention by braking the trailer or semitrailer if a transverse force acts on the semitrailer or trailer in the direction of an increase in the buckling angle or if the angle of inclination and the buckling angle have the same operational sign. Detection of transverse force and angle of inclination are described in, for example, German Published Patent Application No. 40 26 627 and German Published Patent Application No. 40 30 653. The transverse force is the actual quantity to be analyzed. However, since the transverse force can be determined only in a relatively complicated procedure, the angle of inclination is instead used as an xe2x80x9cequivalent quantityxe2x80x9d and an angle of inclination is determined for the trailer or semitrailer.
Tire force sensors or sidewall sensors are known. These involve vehicle tires having magnetic surfaces vulcanized into the side walls. These magnetic surfaces pass by induction sensors during rotation of the tire, thereby generating electrical signals. With an appropriate analysis, the transverse forces prevailing on the individual tires, among other things, can be determined from these signals.
If the information about the transverse force is available, then the method and the device according to the present invention can be simplified so that no buckling angle sensor is used. Instead, the buckling angle would be determined as follows: the yaw rate of the semitrailer is determined from the transverse force. This requires, in addition to the transverse force acting on the semitrailer, the float angle of the tractor vehicle, the buckling angle (of the preceding increment of time), the yaw rate of the tractor vehicle plus various geometric quantities. The buckling rate is determined from the yaw rate of the semitrailer and the yaw rate of the tractor vehicle (measured with the yaw rate sensor). Then the buckling angle is calculated from the buckling rate by integration. This value of the buckling angle is taken into account in the next time increment.
In another advantageous embodiment of the present invention, the trailer or semitrailer is braked if:
{dot over ("psgr")}z greater than {dot over ("psgr")}z*, when xcex94"psgr" greater than 0
or
{dot over ("psgr")}z less than {dot over ("psgr")}z*, when xcex94"psgr" less than 0
where
{dot over ("psgr")}z is the yaw rate of the tractor vehicle and
{dot over ("psgr")}z*is the setpoint yaw rate of the tractor vehicle.
An example of calculating the setpoint yaw rate of the tractor vehicle from the velocity of the combination and the steering angle has been published in the article xe2x80x9cFDRxe2x80x94die Fahrdynamikreglung von Bosch [FDRxe2x80x94Driving Dynamics Control from Bosch]xe2x80x9d by A. van Zanten, R. Erhardt and G. Pfaff, in the automotive engineering journal ATZ Automobiltechnische Zeitschrift, 96 (1994) 11, pp. 674-689 and the article xe2x80x9cVehicle Dynamics Controller for Commercial Vehiclesxe2x80x9d by F. Hecker, S. Hummel, O. Jundt, K.-D. Leimbach, I. Faye, H. Schramm, SAE Paper 973284.
In an especially advantageous embodiment of the present invention, the braking process is terminated, in particular immediately after a change in the operational sign of the buckling rate. The combination is stabilized especially well by this measure. By analysis of the buckling rate, the vehicle is prevented from becoming unstable again because of intervention measures that last too long under some circumstances.
As an alternative, a check is performed to determine whether the value of the buckling rate is in a small range around zero. This range is defined by a small value KG1, i.e., the range corresponds to the interval from xe2x88x92KG1 to +KG1. Consequently, braking of the trailer or semitrailer is terminated when the buckling rate is less than +KG1 for a positive buckling rate, or when the buckling rate is greater than xe2x88x92KG1 for a negative buckling rate.
In an especially advantageous embodiment, the present invention works together with a vehicle stabilization system such as that described, for example, in the articles xe2x80x9cFDRxe2x80x94Driving Dynamics Control from Boschxe2x80x9d by A. van Zanten, R. Erhardt and G. Pfaff, ATZ Automobiltechnische Zeitschrift, 96 (1994) 11, pp. 674-689 and the article xe2x80x9cVehicle Dynamics Controller for Commercial Vehiclesxe2x80x9d by F. Hecker, S. Hummel, O. Jundt, K.-D. Leimbach, I. Faye, H. Schramm, SAE Paper 973284.
In another advantageous embodiment of the present invention, the at least one trailer or semitrailer is braked essentially the same on both sides.
In an advantageous embodiment, the tractor vehicle is equipped with the sensors used as part of vehicle dynamics control (see xe2x80x9cVehicle Dynamics Controller for Commercial Vehiclesxe2x80x9d by F. Hecker, S. Hummel, O. Jundt, K.-D. Leimbach, I. Faye, H. Schramm, SAE Paper 973284). Furthermore, the vehicle combination has a buckling angle sensor. The transverse force is calculated, for example, as a function of the yaw rate and the float angle of the tractor vehicle and various geometric parameters.
In an alternative embodiment, the tractor vehicle is equipped with sensors used as part of driving dynamics control. The vehicle combination does not have a buckling angle sensor. The vehicle combination has tire force sensors. The buckling angle is calculated as described above on the basis of the signals supplied by the tire force sensors.
In another alternative embodiment, the vehicle is equipped with the sensors used as part of driving dynamics control. Furthermore, the vehicle combination is equipped with a buckling angle sensor and tire force sensors.
The present invention can be used for hydraulic, electrohydraulic, pneumatic, electropneumatic or electromechanical brake systems.